Data mining in a digital map database to identify traffic signals, stop signs and yield signs at bottoms of hills and enabling precautionary actions in a vehicle

ABSTRACT

Disclosed is a feature for a vehicle that enables taking precautionary actions in response to conditions on the road network around or ahead of the vehicle, in particular, a traffic light, stop sign or yield sign located at the bottom of a hill. A database that represents the road network is used to determine locations where a traffic light, stop sign or yield sign is located at the bottom of a hill. Then, precautionary action data is added to the database to indicate a location at which a precautionary action is to be taken about the traffic light, stop sign or yield sign located at the bottom of a hill. A precautionary action system installed in a vehicle uses this database, or a database derived therefrom, in combination with a positioning system to determine when the vehicle is at a location that corresponds to the location of a precautionary action. When the vehicle is at such a location, a precautionary action is taken by a vehicle system as the vehicle is approaching a traffic light, stop sign or yield sign located at the bottom of a hill.

REFERENCE TO RELATED APPLICATION

The present patent application is related to the copending patentapplication Ser. No. 12/156,264, filed on the same date, entitled “DATAMINING TO IDENTIFY LOCATIONS OF POTENTIALLY HAZARDOUS CONDITIONS FORVEHICLE OPERATION AND USE THEREOF,”, the entire disclosure of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a method and system that enables takinga precautionary action in a vehicle, such as providing a warning to avehicle driver about a potentially difficult or hazardous drivingcondition on the road network.

Advanced driver assistance systems (“ADAS”), including active safety andfuel economy systems, have been developed to improve the comfort,efficiency, safety, and overall satisfaction of driving. Examples ofthese advanced driver assistance systems include adaptive headlightaiming, adaptive cruise control, lane departure warning and control,curve warning, speed limit notification, hazard warning, predictivecruise control, and adaptive shift control, as well as others. Some ofthese advanced driver assistance systems use a variety of sensormechanisms in the vehicle to determine the current state of the vehicleand the current state of the roadway in front of the vehicle. Thesesensor mechanisms may include radar, infrared, ultrasonic andvision-oriented sensors, such as digital video cameras and lidar. Someadvanced driver assistance systems also use digital map data. Digitalmap data can be used in advanced driver assistance systems to provideinformation about the road network, road geometry, road conditions andother items associated with the road and terrain around the vehicle.Digital map data is not affected by environmental conditions, such asfog, rain or snow. In addition, digital map data can provide usefulinformation that cannot reliably be provided by cameras or radar, suchas curvature, grade, bank, speed limits that are not indicated bysignage, traffic and lane restrictions, etc. Further, digital map datacan provide a predictive capability well beyond the range of othersensors or even beyond the driver's vision to determine the road aheadof the vehicle, around corners, over hills or beyond obstructions.Accordingly, digital map data can be a useful addition for some advanceddriver assistance systems.

Although these kinds of systems provide useful features, there existsroom for further improvements. For example, it would be useful toidentify locations on the road network where a relatively high number oftraffic accidents have occurred. However, statistics pertaining toaccidents are maintained by various different administrative entitiesthat use different formats, standards, reporting methods, reportingperiods, etc. Accordingly, it is difficult to obtain consistentinformation about traffic accidents on roads in a large geographicregion, such as the entire United States or Europe. Moreover, dataindicating locations where a statistically large number of trafficaccidents occur may not indicate the causes of the accidents or howaccidents can be avoided.

Accordingly, it is an objective to provide a system that facilitatestaking a precautionary action in a vehicle, such as providing a warningto a vehicle operator, when approaching a location where a trafficsignal, stop sign or yield sign is located at the bottom of a hill.

SUMMARY OF THE INVENTION

To address these and other objectives, the present invention comprises afeature that enables taking a precautionary action in a vehicle as thevehicle approaches a traffic light, stop sign or yield sign located atthe bottom of a hill. The precautionary action may be a warning messageprovided to the vehicle driver to alert the vehicle driver about thetraffic light, stop sign or yield sign so that the vehicle driver canpay extra attention. Alternatively, the precautionary action may be anactual modification of the operation or control of the vehicle, such asbraking, accelerating, or maneuvering the vehicle, or activating asensor. Alternatively, the precautionary action may be providing aninput to an algorithm that also processes inputs from other sensors fortaking such actions. In another alternative, the precautionary actionmay include a combination of any of these aforementioned actions.

According to another aspect, a database that represents the road networkis used to determine locations where a traffic light, stop sign or yieldsign is located at the bottom of a hill. Then, precautionary action datais added to the database to indicate a location at which a precautionaryaction is to be provided about the traffic light, stop sign or yieldsign is located at the bottom of a hill.

According to further aspects, a precautionary action system installed ina vehicle uses this database, or a database derived therefrom, incombination with a positioning system, to determine when the vehicle isat a location that corresponds to the location where a precautionaryaction should be taken. When the vehicle is at such a location, theprecautionary action is taken, such as providing a warning to thevehicle operator, as the vehicle is approaching a traffic light, stopsign or yield sign located at the bottom of a hill. Alternatively, theprecautionary action may consist of an actual modification of theoperation or control of the vehicle, such as braking, accelerating, ormaneuvering the vehicle, or activating a sensor. Alternatively, theprecautionary action may include providing an input to an algorithm thatalso processes inputs from other sensors for taking such actions.Alternatively, the precautionary action may be adjustment ofsensitivities of other ADAS applications such as increasing the controlauthority and sensitivity of a lane departure warning or control systemto lane edge approach and violation. In another alternative, theprecautionary action may include a combination of any of theseaforementioned actions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a portion of a road network with a stopsign located at the bottom of a hill.

FIG. 2 is a flowchart of a process that uses a database that representsa road network to identify conditions such as the one shown in FIG. 1.

FIG. 3 is a diagram of a data record formed by the process of FIG. 2.

FIG. 4 is a diagram of a vehicle system that uses data produced by theprocess of FIG. 2.

FIG. 5 is a flowchart of a process performed by the system of FIG. 4.

DETAILED DESCRIPTION OF THE DESCRIPTION OF THE PRESENTLY PREFERREDEMBODIMENTS

FIG. 1 depicts road segments 10, 12, 14 and 16. These road segments meetat an intersection 20. The road segment 10 is located on a hill 22, suchthat the altitude of one end 24 of the road segment 10 is greater thanthe altitude at the other end 26, which in this case is the end at theintersection 20. Located at the intersection 20 are stop signs 28 and30.

FIG. 2 is a flowchart of a process 100. The process 100 is performed bya software program or routine that is run on a suitable computingplatform, such as a database server, PC or plurality of PCs coupledtogether for parallel computing applications.

The process 100 uses a database 110 that contains data that representsthe road network in a region. The region may be a country, such as theUnited States, Germany, France or Korea. Alternatively, the region mayinclude several countries or an entire continent. According to anotheralternative, the region may include only a portion of a country, such asa state or several states or metropolitan areas.

The process 100 is performed by a map developer, such as NAVTEQCorporation. Alternatively, the process 100 may be performed by anotherentity that has access to an editable version of a map database 110. Forexample, the process may be performed by a customer or licensee ofNAVTEQ, such as a manufacturer of navigation systems or active safetysystems, or by a traffic information services company or by a governmentoffice at any level.

The database 110 is in a format that can be edited. That is, new orupdated information can be added to the database 110. Alternatively, thedatabase 110 is in a format such that new information can be combinedwith the original data to form a new database that includes both theoriginal data and new data. In one embodiment, the database is in anOracle spatial format. Alternatively, the database may be in deliveryformat, such as GDF (Geographic Data File), SIF (Standard InterchangeFormat), or other formats, including proprietary formats.

As stated above, the database 110 contains data that represents the roadnetwork in the region. The database 110 contains information such as thelocations (geographic coordinates, including altitude) of roads andintersections, road names, the three-dimensional shape of the roadsincluding curvature, slope and bank, speed limits along roads, turnrestrictions at intersections, addresses or address ranges along roads,the number of lanes each road has, lane width, traffic control featuressuch as traffic signals, stop signs and yield signs, lane markings,functional classes of roads, the locations of medians, and so on. Thedatabase may also contain information about other geographic features,such as bodies of water, parks, administrative areas (includingmunicipal, state and country boundaries), and locations of points ofinterest, such as businesses, hospitals, police stations, and so on.

In FIG. 2, the process 100 examines each data record that represents aroad segment (also referred to herein as a “link”) to determine whetherit represents one similar to the road segment 10 in FIG. 1. (The process100 may use a procedure that examines in turn each data record thatrepresents each road segment represented in the entire database.) In onestep, a data record that represents a link or road segment is read fromthe database 110 (Step 130). This road segment record includes dataattributes that indicate the altitude at each end (i.e., the nodes) ofthe represented road segment. The altitudes at the ends of therepresented road segment are compared (Step 134). From the comparison ofaltitude information, it can be determined whether the represented roadsegment is part of a hill. If the represented road segment is not partof a hill, the process 100 proceeds to a step in which it is determinedwhether all the road segment records in the database have been examined(Steps 136 and 138). If there are more segment records to examine, theprocess 100 proceeds to get the next segment record (Step 130) andcontinues.

Referring back to Step 136, if the represented road segment is part of ahill, the process 100 proceeds to obtain the data that represent trafficsignals, stop signs or yield signs along the segment (Step 142). Thedata that represent traffic lights, stop signs or yield signs isexamined (Step 144). From an examination of segment's altitude change,as well as the data that represent traffic lights, stop signs and yieldsigns, it is determined whether there exists a traffic light, stop signor yield sign at the bottom of a hill (similar to the stop sign 28 shownin FIG. 1). If examination of the segment's altitude change and the datathat represent traffic lights, stop signs and yield signs indicates thatthere is no traffic light, stop sign or yield sign at the bottom of ahill, the process 100 proceeds to the step in which it is determinedwhether all the road segment records in the database have been examined(Steps 150 and 138) and if there are more segment records to examine,the process 100 proceeds to get the next segment record (Step 130).

Referring back to Step 150, if examination of the segment's altitudechange and the data that represent traffic lights, stop signs and yieldsigns indicates that there is a traffic light, stop sign or yield signat the bottom of a hill, the process 100 adds precautionary action data160 to the database 110 (Step 156). The precautionary action data 160indicates the presence of a feature in the road network where aprecautionary action may be taken. After the precautionary action data160 is added to the database 110, the process 100 proceeds to the stepin which it is determined whether all the road segment records in thedatabase have been examined (Step 138) and if there are more segmentrecords to examine, the process 100 proceeds to get the next segmentrecord (Step 130).

The process 100 ends when it is determined whether all the road segmentrecords have been examined (Step 138).

It is noted that the process 100, above, performs a data miningfunction. The existence of the potentially difficult location, i.e., thepresence of a traffic light, stop sign or yield sign located at thebottom of a hill, is derived from data already collected and present inthe database. It is noted that the process 100, above, evaluatesmultiple data items in the original database, to determine whether thecondition exists, in this case, a traffic light, stop sign or yield signlocated at the bottom of a hill. By evaluating these multiple dataitems, a determination is made whether these multiple data itemsdescribe the condition of interest. If these data items do describe thecondition, a new data item, i.e., the precautionary action data, isadded to the database.

It is further noted that the process 100 may use a threshold whenevaluating various items of data to determine whether the potentiallyhazardous condition exists. For example, the relative amount ofelevation change along a road segment may be compared to a threshold(e.g., 3%) to determine whether a traffic light, stop sign or yield signlocated one end of the road segment is at the bottom of a hill.

FIG. 3 is a diagram that shows a data record 200 in the database 110.The data record 200 represents a road segment located in a geographicregion. As explained above, the geographic region may include an entirecountry or continent. Accordingly, the database 110 includes many datarecords like the one shown in FIG. 3.

The data record 200 shown in FIG. 3 is exemplary and shows only one wayto represent a road segment. Databases may represent road segments invarious different ways and may include different kinds of information.The present invention is not limited to any particular way ofrepresenting roads.

Referring to FIG. 3, various data are associated with the data record200 that represents a road segment. This various data indicates featuresor attributes of the represented road segment. For example, associatedwith the data record is data that indicates the permitted direction(s)of travel. Also associated with the road segment record 200 are datathat indicate a speed limit, a classification of the road segment (i.e.,the type of road, such as controlled access, etc.), a rank (e.g., 1-4),the endpoints of the road segment, shape points (i.e., locations alongthe road segment between its endpoints). Also associated with the roadsegment records is data that indicate the successors at each endpoint.Successors are those road segments that connect to the represented roadsegment at each of its endpoints. The segment record 200 may identifythese successors by reference to the data records that represent thesuccessors.

In FIG. 3, the database 110 also includes precautionary action data 160.The precautionary action data 160 is the data added to the database 110by the process 100 in FIG. 2. In FIG. 3, the precautionary action data160 is shown as added to the road segment record 200. It should beunderstood that the process 100 adds precautionary action data 160 withrespect to only certain records, i.e., records that represent thoseroads segments that meet the conditions identified by the process.Accordingly, the database 110 will contain data records that representroad segments that contain the precautionary action data 160 and otherdata records that represent road segments that do not contain theprecautionary action data 160.

In the embodiment shown in FIG. 3, the precautionary action data 160 isassociated with the road segment identified as being part of a hill andleading to a traffic light, stop sign or yield sign located at thebottom of a hill. In this embodiment, the precautionary action data 160includes several components. One component 160(1) indicates a conditiontype. This condition type 160(1) indicates the type of condition aboutwhich a precautionary action is to be taken, which in this case is atraffic light, stop sign or yield sign located at the bottom of a hill.This condition type 160(1) component is used when different conditionsare identified in the database 110 about which precautionary action maybe taken.

Another component of the precautionary action data 160 is theprecautionary action location 160(2). The precautionary action location160(2) indicates where along the represented road segment aprecautionary action may be taken. The precautionary action location160(2) data may include multiple entries. For example, the precautionaryaction location 160(2) may indicate where a warning may be provided to avehicle driver to advise the driver about the upcoming condition, i.e.,the traffic light, stop sign or yield sign located at the bottom of ahill. In the case of a traffic light, stop sign or yield sign located atthe bottom of a hill, the warning location 160(2) may indicate adistance (e.g., x meters) from the traffic light, stop sign or yieldsign. The location 160(2) is determined based on an analysis of factors,such as the slope of the hill, the speed limit along the representedroad segment, the road classification, and possibly other factors. Thesefactors may be determined from other data contained in the database 110.According to one example, the location 160(2) may indicate that awarning should be provided at a location 400 meters along the roadsegment from the downhill traffic light, stop sign or yield sign.

The precautionary action location 160(2) may also indicate where avehicle control action should be taken, such as tightening theseatbelts, pre-loading or engaging the brakes, tightening sensitivitiesof lane departure warning systems or stability control systems, etc.This may be a different location from where the precautionary warning isprovided and would be based on a different analysis of factors.

Another component of the precautionary action data 160 is direction data160(3). The direction data 160(3) indicates the direction along therepresented road segment where the precautionary action should be taken.In this case, the direction data 160(3) indicates the downhilldirection. (Note that the database 110 may indicate a direction along aroad segment as positive or negative based on the relative latitude andlongitude of the road segment endpoints. Accordingly, the downhilldirection may be indicated as positive or negative.)

Another component of the precautionary action data 160 is a reference160(4). In this case, the reference 160(4) indicates the location of thetraffic light, stop sign or yield sign located at the bottom of a hill.

The precautionary action data 160 described in FIG. 3 is one way thatthis data may be included in a database that represents a geographicregion. There are alternative ways to include the precautionary actiondata. For example, the precautionary action data may be included asseparate data records in the database 110. If included as separate datarecords, the precautionary action data may be associated with the roadsegments to which they apply by pointers or other suitable datareferences. Alternatively, the precautionary action data may beassociated with node data records, i.e., the data that represent theintersections, instead of the road segments leading to theintersections. Various other ways exist and the present invention is notintended to be restricted to any specific implementation.

FIG. 4 is a diagram depicting components of a vehicle 300. The vehicle300 is operated on a road network, such as the road network representedby the database 110 in FIG. 2. The vehicle 300 may be an automobile,truck, bicycle, motorcycle, etc.

The vehicle 300 includes systems 310. In this embodiment, the vehiclesystems 310 include a positioning system 320. The positioning system 320determines the position of the vehicle 300 on the road network. Thepositioning system 320 includes appropriate hardware and software todetermine the position of the vehicle 300. For example, the positioningsystem may include hardware 322 that includes a GPS unit, anaccelerometer, wheel speed sensors, etc. The positioning system 320 alsoincludes a positioning application 324. The positioning application 324is a software application that uses outputs from the positioning systemhardware 322 and information from a map database 330. The positioningapplication 324 determines the position of the vehicle 300 with respectto the road network, including the location of the vehicle 300 along aroad segment and a direction of travel of the vehicle along the roadsegment.

In one embodiment, the map database 330 is located in the vehicle. In analternative embodiment, the map database 330 may be located remotely andaccessed by the vehicle systems 310 using a wireless communicationsystem. In yet another embodiment, part of the map database 330 may belocated locally in the vehicle and part of the map database 330 may belocated remotely.

The map database 330 is stored on a computer readable medium 334. Thecomputer-readable medium may be implemented using any suitabletechnology. For example, the computer readable medium may be a DVD disk,a CD-ROM disk, a hard disk, flash memory, or any other medium, or aplurality of media.

The map database 330 includes data that represents the geographic regionin which the vehicle 300 is being operated. The map database 330 mayrepresent the same geographic region as the database 110 in FIG. 2, oralternatively, the map database 330 may represent only a portion of theregion represented by the database 110.

The map database 330 used by the vehicle systems 310 may be in adifferent format from the database 110 in FIG. 2. The map database 330is formed or derived from the database 110 by a compilation process thatorganizes and presents the data in a form and format that specificallyfacilitates its use for performing specific functions. For example, themap database 330 may be separated into different collections of datathat are used for specific functions, such as vehicle positioning, routecalculation, map display, route guidance, destination selection, and soon. The map database 330 may also be organized into groupings spatially.One kind of compiled database format is disclosed in U.S. Pat. No.5,968,109, the entire disclosure of which is incorporated by referenceherein. Various other compiled database formats exist, includingproprietary formats, and the disclosed embodiment(s) are not limited toany particular format.

Included among the vehicle systems 310 in FIG. 4 is a navigation system340. The navigation system 340 uses outputs from the positioning system320 and data from the map database 330 to provide navigation-relatedfeatures to a vehicle user, e.g., the vehicle operator or passenger. Thenavigation system 340 includes applications for route calculation 344,map display 346, as well as possibly other applications. The navigationsystem 340 provides the navigation-related features to the vehicle uservia a user interface 354. (The navigation system 340 is optional and maybe omitted.)

Also included among the vehicle systems 310 is a precautionary actionapplication 350. The precautionary action application 350 uses outputsfrom the positioning system 320 and data from the map database 330 totake precautionary actions, such as provide warnings to the vehicleoperator. The precautionary action application 350 provides the warningto the vehicle operator via the user interface 354.

FIG. 4 also shows that precautionary action application 350 provides anoutput to vehicle control systems and actuator 356. The vehicle controlsystems and actuator are operatively connected to various vehiclemechanical systems, such as the vehicle's brakes 356(1), engine 356(2),seatbelts (including tensioners) 356(3), airbags 356(4), stabilitycontrol algorithms, as well as other system systems 356(5).

FIG. 5 is a flowchart 400 showing operation of the precautionary actionapplication 350 (in FIG. 4). As the vehicle 300 (in FIG. 4) is beingoperated on a road, the precautionary action application 350 obtains thecurrent vehicle position from the positioning system 320 (Step 410).(During vehicle operation, the positioning system 320 continuouslydetermines the current geographic position of the vehicle 300 as thevehicle is being operated using data from the map database 330.) Thepositioning system 320 provides the precautionary action applicationwith data that indicates the current vehicle position with respect tothe road network as represented by the map database 330. Specifically,the location of the vehicle along a road segment and the direction oftravel of the vehicle along the road segment are determined and providedto the precautionary action application 350.

Next, the process 400 obtains data from the map database 300 thatrepresents the geographic features (i.e., roads, intersections, etc.) atthe current location of the vehicle and in the direction in which thevehicle is heading (Step 420). In one embodiment, an electronic horizonis used (Step 430). Building an electronic horizon and using it toprovide warnings are disclosed in U.S. Pat. Nos. 6,405,128 and 6,735,515and U.S. patent application Ser. No. 11/400,151, the entire disclosuresof which are incorporated by reference herein. Using an electronichorizon and/or the inventions disclosed in these patents and pendingpatent application is optional and the disclosed process 400 is notlimited to using the electronic horizon technology.

After obtaining data from the map database 300 that represents thegeographic features at the current location of the vehicle and in thedirection in which the vehicle is heading, the process 400 includes thestep of examining the data to determine whether any precautionary actiondata (160 in FIG. 3) is associated with the represented geographicfeatures (Step 440). If there is no precautionary action data associatedwith the represented geographic features, the process 400 loops back toget a new current vehicle position (Step 410). On the other hand, ifthere is precautionary action data associated with the representedgeographic features, the process 400 takes a precautionary action (Step450). The precautionary action may be a warning provided to the vehicleoperator when the vehicle is at the location (i.e., 160(2) in FIG. 3)indicated by the precautionary action data. The warning may be providedvia the user interface 354. The warning may be an audible warningmessage or a visual warning.

The precautionary action is not limited to warnings, but may alsoinclude other actions. For example, in the case of a traffic light, stopsign or yield sign located at the bottom of a hill, vehicle systems 356,such as the brakes, engine or transmission, can be readied for a quickdeceleration or stop. In addition, the seatbelts may be tightened or theairbags set to deploy. As explained above, to facilitate these kinds ofactions, additional information may be added to the warning data 160 (inFIG. 3) to indicate the type of action as well as the location where theaction should be taken.

Referring still to FIG. 5, after taking the precautionary action, theprocess 400 loops back to get a new current vehicle position (Step 410).

Alternative with Dynamic Data

The process (400 in FIG. 5) was described as a way to use theprecautionary action data that had been stored in the map database totake an appropriate action in a vehicle when the vehicle is at or isapproaching a location identified as having a potentially hazardouscondition. This process uses a positioning system and map database inthe vehicle to determine when the vehicle is at or is approaching such alocation. The process may also take into account dynamic information.Dynamic information may include current traffic and weather conditions,ambient light conditions, road conditions (e.g., ice), and so on. Thevehicle may include systems to obtain such information. For example, thevehicle may have a traffic data receiver that obtains real-time trafficinformation, e.g., RDS-TMC messages. The process 400 may use the dynamicinformation in combination with the precautionary action data. Forexample, the process may modify the location at which a warning isprovided. As an example, if weather conditions indicate that it israining, the location at which a warning is provided to the vehicledriver about a traffic light, stop sign or yield sign located at thebottom of a hill may be modified, i.e., adjusted to a point farther inadvance of the location of the hazardous condition, in order to give thevehicle operator additional time or distance. The process may even takecertain actions only under certain conditions. For example, a warningabout traffic light, stop sign or yield sign located at the bottom of ahill may be provided only during nighttime hours. During daylight, thecondition may not warrant a warning.

Verification

The process (100 in FIG. 2) was described as a way to automaticallyexamine records in a database that represents roads to identifylocations or conditions along the road network where a precautionaryaction might be taken. According to the described process, data is thenadded to indicate the location where the precautionary action should betaken. Alternatively, instead of automatically adding the precautionaryaction data to the database, the locations where such conditions areidentified could be marked on a temporary basis. Then, a geographicanalyst (or other human operator) could review some or all suchtemporarily marked locations. The analyst may conduct this review byphysically traveling to the locations or by reviewing satellite oraerial photographs of the locations, or video taken while driving by thelocations (previously or subsequently acquired either by the analyst orothers including members of the public). Based on the review, theanalyst then determines whether precautionary action data should beadded to the database.

It is intended that the foregoing detailed description be regarded asillustrative rather than limiting and that it is understood that thefollowing claims including all equivalents are intended to define thescope of the invention.

1. A method for making an augmented version of a database that can beused as a component in a vehicle system that provides a precautionaryaction in a vehicle when the vehicle approaches a potentially hazardouslocation, wherein the potentially hazardous location is one in which twoconditions are present at a same location along a road network in ageographic region, wherein one of the two conditions comprises presenceof a traffic light, stop sign or yield sign and another of the twoconditions comprises a bottom of a hill, the method comprising: usingdata contained in a first version of the database to identify trafficlights, stop signs or yield signs located at the bottoms of hillsthroughout the geographic region; and forming the augmented version ofthe database by adding precautionary action data to the first version ofthe database to indicate locations at which a precautionary action is tobe taken by the vehicle system.
 2. The method of claim 1 furthercomprising: selecting from the first version of the database a datarecord that represents a road segment; upon determining that the roadsegment is part of a hill, obtaining data that represent traffic lightsstop signs or yield signs along the road segment; and upon determiningthat the road segment is part of a hill and that a traffic light, stopsign or yield sign is located at a bottom of the hill, adding theprecautionary action data to the first version of the database toindicate the presence of a condition for which a precautionary action isto be taken.
 3. The method of claim 2 further wherein the road segmentis determined to be part of a hill by comparing the altitudes at theendpoints of the road segment.
 4. The method of claim 2 furthercomprising: continuing to select from the first version of the databasedata records that represent road segments to identify all locations oftraffic lights, stop signs or yield signs located at bottoms of hillsthroughout the geographic region.
 5. The method of claim 2 furthercomprising: continuing to select from the first version of the databasedata records that represent road segments until all data records thatrepresent road segments have been selected.
 6. The method of claim 1further comprising: compiling the augmented version of the database intoa format suitable for use in a navigation system.
 7. The method of claim1 wherein the step of using data contained in the first version of thedatabase comprises evaluating at least two items of data contained inthe first version of the database to determine whether a traffic light,stop sign or yield sign is located at a bottom of a hill.
 8. A databasestored on a computer-readable medium, wherein the database includes datathat represents a road network in a geographic region, wherein thedatabase comprises: data records that represent road segments that makeup the road network; data that indicates altitude of the road segments;and data that indicates precautionary action locations, wherein aprecautionary action location is associated with a location where twoconditions are present at a same location, wherein one of the twoconditions comprises a traffic light, stop sign or yield sign andanother of the two conditions is a bottom of a hill.
 9. The database ofclaim 8 wherein the precautionary action data further includes data thatindicates a location along a road segment at which a precautionaryaction is to be taken by a vehicle system.
 10. The database of claim 8wherein the precautionary action data further includes data thatindicates a direction along a road segment at which a precautionaryaction is to be taken.
 11. The database of claim 8 wherein theprecautionary action data further includes data that refers to thelocation of the actual traffic light, stop sign or yield sign located atthe bottom of the hill.
 12. The database of claim 8 further comprisingdata that indicates permitted directions of travel along road segments,speed limits along road segments, classifications of road segments, andlocations of road segments.
 13. The database of claim 8 furthercomprising data that identifies successor road segments of each roadsegment, wherein successor road segments are those road segments thatconnect to a road segment at each end thereof.
 14. A vehicle systemcomprising: a database that contains data representing a geographicregion in which a vehicle is being operated, wherein the data includesdata that represents a road network located in the geographic region andprecautionary action data that indicates precautionary action locationsassociated with locations where traffic lights, stop signs or yieldsigns are located at bottoms of hills; a positioning system thatdetermines a current location of the vehicle relative to the datarepresenting a geographic region; and a precautionary action applicationresponsive to the positioning system and the database that provides aprecautionary action when the positioning system determines that thecurrent location of the vehicle is approaching a traffic light, stopsign or yield sign located at a bottom of a hill.
 15. The system ofclaim 14 wherein the precautionary action data further includes datathat indicates a location along a road segment at which a precautionaryaction is to be taken by a vehicle system.
 16. The system of claim 14wherein the precautionary action data further includes data thatindicates a direction along a road segment at which a precautionaryaction is to be taken.
 17. The system of claim 14 wherein theprecautionary action data further includes data that refers to thelocation of the actual traffic light, stop sign or yield sign located atthe bottom of a hill.
 18. A method for providing precautionary actionsin a vehicle comprising: accessing a database that represents a roadnetwork, determining a current position of the vehicle relative to theroad network represented by the database; upon determining that datarepresentations of a part of the road network around the currentposition of the vehicle include precautionary action data, taking aprecautionary action as the vehicle is approaching a traffic light, stopsign or yield sign located at a bottom of a hill.
 19. The method ofclaim 18 further comprising: building an electronic horizon afteraccessing the database; and using the electronic horizon to determinewhether precautionary action data is included therein.
 20. The method ofclaim 18 wherein the precautionary action is provided via a userinterface of the vehicle.